Streams debugging within a windowing condition

ABSTRACT

Method, system and computer program product for performing an operation, the operation including providing a plurality of processing elements comprising one or more operators, the operators configured to process streaming data tuples. The operation then establishes an operator graph of multiple operators, the operator graph defining at least one execution path in which a first operator of the plurality of operators is configured to receive data tuples from at least one upstream operator and transmit data tuples to at least one downstream operator. The operation then defines a breakpoint, the breakpoint comprising a condition, the condition based on attribute values of data tuples in a window of at least one operator, the window comprising a plurality of data tuples in an operator. The operation, upon detecting occurrence of the condition, triggers the breakpoint to halt processing by each of the plurality of operators in the operator graph.

BACKGROUND

Embodiments of the present disclosure generally relate to streamcomputing applications using streaming data. Specifically, theembodiments disclose techniques for defining and triggering breakpointsto debug streams applications that use streaming data.

SUMMARY

Embodiments disclosed herein provide a method, system and computerprogram product for performing an operation, the operation includingproviding a plurality of processing elements comprising one or moreoperators, the operators configured to process streaming data tuples.The operation then establishes an operator graph of multiple operators,the operator graph defining at least one execution path in which a firstoperator of the plurality of operators is configured to receive datatuples from at least one upstream operator and transmit data tuples toat least one downstream operator. The operation then defines abreakpoint, the breakpoint comprising a condition, the condition basedon attribute values of data tuples in a window of at least one operator,the window comprising a plurality of data tuples in an operator. Theoperation, upon detecting occurrence of the condition, triggers thebreakpoint to halt processing by each of the plurality of operators inthe operator graph.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited aspects are attained andcan be understood in detail, a more particular description ofembodiments of the disclosure, briefly summarized above, may be had byreference to the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIGS. 1A-1B illustrate a computing infrastructure configured to executea stream computing application, according to embodiments disclosedherein.

FIG. 2 is a more detailed view of the compute node of FIGS. 1A-1B,according to one embodiment disclosed herein.

FIG. 3 is a more detailed view of the server management system of FIGS.1A-1B, according to one embodiment disclosed herein.

FIG. 4 is a flowchart depicting a method for streams debugging within awindowing condition, according to one embodiment disclosed herein.

FIG. 5 is a flowchart depicting a method for defining a timingbreakpoint, according to one embodiment disclosed herein.

FIG. 6 is a flowchart depicting a method for defining timing breakpointconditions, according to one embodiment disclosed herein.

FIG. 7 illustrates a table depicting whether operator window contentswill trigger a timing breakpoint, according to one embodiment disclosedherein.

DETAILED DESCRIPTION

Embodiments disclosed herein provide a method, system and computerprogram product for performing an operation, the operation includingproviding a plurality of processing elements comprising one or moreoperators, the operators configured to process streaming data tuples.The operation then establishes an operator graph of multiple operators,the operator graph defining at least one execution path in which a firstoperator of the plurality of operators is configured to receive datatuples from at least one upstream operator and transmit data tuples toat least one downstream operator. The operation then defines abreakpoint, the breakpoint comprising a condition, the condition basedon attribute values of data tuples in a window of at least one operator,the window comprising a plurality of data tuples in an operator. Theoperation, upon detecting occurrence of the condition, triggers thebreakpoint to halt processing by each of the plurality of operators inthe operator graph.

In the following, reference is made to embodiments of the disclosure.However, it should be understood that the disclosure is not limited tospecific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practice thedisclosure. Furthermore, although embodiments of the disclosure mayachieve advantages over other possible solutions and/or over the priorart, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the disclosure. Thus, the followingaspects, features, embodiments and advantages are merely illustrativeand are not considered elements or limitations of the appended claimsexcept where explicitly recited in a claim(s). Likewise, reference to“the invention” shall not be construed as a generalization of anyinventive subject matter disclosed herein and shall not be considered tobe an element or limitation of the appended claims except whereexplicitly recited in a claim(s).

Stream-based computing and stream-based database computing are emergingas a developing technology for database systems. Users may createapplications that process and query streaming data before it reaches adatabase file. Users can specify processing logic to apply to inbounddata records while they are “in flight,” with the results available in avery short amount of time, often in milliseconds. Constructing anapplication using this type of processing has opened up a newprogramming paradigm that will allow for a broad variety of innovativeapplications, systems and processes to be developed, as well as presentnew challenges for application programmers and database developers.

In a stream computing application, operators are connected to oneanother such that data flows from one operator to the next (e.g., over aTCP/IP socket). Scalability is reached by distributing an applicationacross nodes by creating executables (i.e., processing elements), aswell as replicating processing elements on multiple nodes and loadbalancing among them. Operators in a stream computing application can befused together to form a larger processing element that is executable,akin to many procedures forming part of a larger program. Doing soallows processing elements to share a common process space, resulting inmuch faster communication between operators than is available usinginter-process communication techniques (e.g., using a TCP/IP socket).Further, processing elements can be split across many nodes in adistributed environment, meaning that scalability can be reached bydistributing an application across nodes by creating many smallexecutable pieces of code.

Debugging code in a streams environment may be accomplished by examininglog files that the code produces. However, in many cases, this simplyisn't enough, and running a debug session is needed. A debug session mayallow users to pinpoint errors which may not be detected by examininglog files alone. An application developer may define breakpoints, theoccurrence of which may trigger the debug session. Often times in adistributed environment, one wants a breakpoint to occur in an operatorwhen events of a similar nature occur simultaneously. In streams ordistributed computing, in general, simultaneous does not mean at theexact same time. In reality, in distributed computing, events cannothappen at the exact same time, but they often occur within a given timeframe of each other. Furthermore, in a streaming data application, theevents triggering a breakpoint may be detected across differentoperators and across multiple operator graphs. Handling events thatoccur within this time frame and allowing breakpoints to take effectwhen events occur within this time frame is the subject of thisdisclosure.

As will be appreciated by one skilled in the art, aspects of the presentdisclosure may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present disclosure may take theform of an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present disclosure may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present disclosure are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of thedisclosure. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

Embodiments of the disclosure may be provided to end users through acloud computing infrastructure. Cloud computing generally refers to theprovision of scalable computing resources as a service over a network.More formally, cloud computing may be defined as a computing capabilitythat provides an abstraction between the computing resource and itsunderlying technical architecture (e.g., servers, storage, networks),enabling convenient, on-demand network access to a shared pool ofconfigurable computing resources that can be rapidly provisioned andreleased with minimal management effort or service provider interaction.Thus, cloud computing allows a user to access virtual computingresources (e.g., storage, data, applications, and even completevirtualized computing systems) in “the cloud,” without regard for theunderlying physical systems (or locations of those systems) used toprovide the computing resources.

Typically, cloud computing resources are provided to a user on apay-per-use basis, where users are charged only for the computingresources actually used (e.g., an amount of storage space used by a useror a number of virtualized systems instantiated by the user). A user canaccess any of the resources that reside in the cloud at any time, andfrom anywhere across the Internet. In context of the present disclosure,a user may access applications or related data available in the cloud.For example, the nodes used to create a stream computing application maybe virtual machines hosted by a cloud service provider. Doing so allowsa user to access this information from any computing system attached toa network connected to the cloud (e.g., the Internet).

FIGS. 1A-1B illustrate a computing infrastructure configured to executea stream computing application, according to one embodiment of thedisclosure. As shown, the computing infrastructure 100 includes amanagement system 105 and a plurality of compute nodes 130 ₁₋₄, eachconnected to a communications network 120. Also, the management system105 includes an operator graph 132 and a stream manager 134. Asdescribed in greater detail below, the operator graph 132 represents astream computing application beginning from one or more operators in oneor more source processing elements (PEs) through to one or moreoperators in one or more sink PEs. This flow from source to sink is alsogenerally referred to herein as an execution path. Generally, dataattributes flow into an operator of a source PE of a stream computingapplication and are processed by that operator. Typically, operatorsreceive an N-tuple of data attributes from the stream as well as emit anN-tuple of data attributes into the stream (except for operators in asink PE where the stream terminates). In general, a “tuple” is a singleinstance of a set of data attributes that follow the formatting of aschema, where the schema establishes a set of typed data attributes thatmay be used. For example, the tuple may be a chunk or portion ofdivisible data such as a data type (e.g., string, integer, Boolean,etc.) or combination of data types. In one embodiment, a “tuple” mayinclude one or more attributes with an assigned value—e.g., Tuple 1:{sym=“Fe”, no=26} where “sym” and “no” are possible attributes in theschema (i.e., a string and integer, respectively) and “Fe” and “26” arethe values.

Of course, the N-tuple received by an operator need not be the sameN-tuple sent downstream. Additionally, operators could be configured toreceive or emit tuples in other formats (e.g., the PEs or operatorscould exchange data marked up as XML documents). Furthermore, eachoperator within a PE may be configured to carry out any form of dataprocessing functions on the received tuple, including, for example,writing to database tables or performing other database operations suchas data joins, splits, reads, etc., as well as performing other dataanalytic functions or operations.

The stream manager 134 may be configured to monitor a stream computingapplication running on the compute nodes 130 ₁₋₄, as well as to changethe deployment of the operator graph 132. The stream manager 134 maymove processing elements (PEs) from one compute node 130 to another, forexample, to manage the processing loads of the compute nodes 130 in thecomputing infrastructure 100. Further, stream manager 134 may controlthe stream computing application by inserting, removing, fusing,un-fusing, or otherwise modifying the processing elements and operators(or what data tuples flow to the processing elements and operators)running on the compute nodes 130 ₁₋₄. One example of a stream computingapplication is IBM®'s InfoSphere® Streams (InfoSphere® is a trademark ofInternational Business Machines Corporation, registered in manyjurisdictions worldwide).

FIG. 1B illustrates an example processing element graph that includesten processing elements (labeled as PE1-PE10) running on the computenodes 130 ₁₋₄. A processing element is composed of one or more operatorsfused together into an independently running process with its ownprocess ID (PID) and memory space. In cases where two (or more)processing elements are running independently, inter-processcommunication may occur using a “transport” (e.g., a network socket, aTCP/IP socket, or shared memory). However, when operators are fusedtogether, the fused operators can use more rapid communicationtechniques for passing tuples among operators in each processingelement.

As shown, the processing element graph begins at a source 135 (thatflows into the processing element labeled PE1) and ends at sink 140 ₁₋₂(that flows from the processing elements labeled as PE6 and PE10).Compute node 130 ₁ includes the processing elements PE1, PE2 and PE3.Source 135 flows into operators in the processing element PE1, which inturn emits tuples that are received by PE2 and PE3. For example,operators in PE1 may split data attributes received in a tuple and passsome data attributes to PE2, while passing other data attributes to PE3.Data that flows to PE2 is processed by the operators contained in PE2,and the resulting tuples are then emitted to the operators in PE4 oncompute node 130 ₂. Likewise, the data tuples emitted by the operatorsin PE4 flow to the operators sink PE6 140 ₁. Similarly, data tuplesflowing from operators in PE3 to operators in PE5 also reach operatorsin sink PE6 140 ₁. Thus, in addition to being a sink for this exampleprocessing element graph, operators in PE6 could be configured toperform a join operation, combining tuples received from operators inPE4 and PE5. This example processing element graph also shows datatuples flowing from PE3 to PE7 on compute node 130 ₃, which itself showsdata tuples flowing to operators in PE8 and looping back to operators inPE7. Data tuples emitted from operators in PE8 flow to operators in PE9on compute node 130 ₄, which in turn emits tuples to be processed byoperators in sink PE10 140 ₂.

Because a processing element is a collection of fused operators, it isequally correct to describe the processing element graph as executionpaths between specific operators, which may include execution paths todifferent operators within the same processing element. FIG. 1Billustrates execution paths between processing elements for the sake ofclarity.

In one embodiment, the stream manger 134 may be able to communicate withother operator graphs executing in a stream computing application. Thatis, the compute nodes 130 may host operator graphs executing inparallel. The stream manager 134 may be able to communicate with astream manager associated with those parallel operator graphs using, forexample, a shared memory where messages and commands may be passed.Alternatively, stream manager 134 may be part of a hierarchicalarrangement of stream managers that allow the different stream managersto communicate. The stream manager 134 may use the manager hierarchy orthe shared memory to instruct a different stream manager to optimize anoperator graph in the stream computing application that is sharing thesame compute nodes 130 (i.e., hardware resources) as the operator graphshown in FIG. 1B. Additionally, the hierarchical arrangement may managestream managers across different compute nodes, for example, a firststream manager 134 for a first stream computing application owned by afirst customer and a second stream manager 134 for a second streamcomputing application owned by a second customer.

FIG. 2 is a more detailed view of the compute node 130 of FIGS. 1A-1B,according to one embodiment disclosed herein. As shown, the compute node130 includes, without limitation, at least one CPU 205, a networkinterface 215, an interconnect 220, a memory 225, and storage 230. Thecompute node 130 may also include an I/O devices interface 210 used toconnect I/O devices 212 (e.g., keyboard, display and mouse devices) tothe compute node 130.

Each CPU 205 retrieves and executes programming instructions stored inthe memory 225. Similarly, the CPU 205 stores and retrieves applicationdata residing in the memory 225. The interconnect 220 is used totransmit programming instructions and application data between each CPU205, I/O devices interface 210, storage 230, network interface 215, andmemory 225. CPU 205 is included to be representative of a single CPU,multiple CPUs, a single CPU having multiple processing cores, and thelike. In one embodiment, a PE 235 is assigned to be executed by only oneCPU 205 although in other embodiments the operators 240 of a PE 235 maycomprise one or more threads that are executed on a plurality of CPUs205. The memory 225 is generally included to be representative of arandom access memory (e.g., DRAM or Flash). Storage 230, such as a harddisk drive, solid state device (SSD), or flash memory storage drive, maystore non-volatile data.

In this example, the memory 225 includes a plurality of processingelements 235. Each PE 235 includes a collection of operators 240 thatare fused together. As noted above, each operator 240 may provide asmall chunk of code configured to process data flowing into a processingelement (e.g., PE 235) and to emit data to other operators 240 in thesame PE or to other PEs in the stream computing application. Suchprocessing elements may be on the same compute node 130 or on othercompute nodes that are accessible via communications network 120.

As shown, storage 230 contains a buffer 260. Although shown as being instorage, the buffer 260 may be located in the memory 225 of the computenode 130 or a combination of both. Moreover, storage 230 may includestorage space that is external to the compute node 130.

FIG. 3 is a more detailed view of the server management system 105 ofFIG. 1, according to one embodiment disclosed herein. As shown, servermanagement system 105 includes, without limitation, a CPU 305, a networkinterface 315, an interconnect 320, a memory 325, and storage 330. Theclient system 130 may also include an I/O device interface 310connecting I/O devices 312 (e.g., keyboard, display and mouse devices)to the server management system 105.

Like CPU 205 of FIG. 2, CPU 305 is configured to retrieve and executeprogramming instructions stored in the memory 325 and storage 330.Similarly, the CPU 305 is configured to store and retrieve applicationdata residing in the memory 325 and storage 330. The interconnect 320 isconfigured to move data, such as programming instructions andapplication data, between the CPU 305, I/O devices interface 310,storage unit 330, network interface 305, and memory 325. Like CPU 205,CPU 305 is included to be representative of a single CPU, multiple CPUs,a single CPU having multiple processing cores, and the like. Memory 325is generally included to be representative of a random access memory.The network interface 315 is configured to transmit data via thecommunications network 120. Although shown as a single unit, the storage330 may be a combination of fixed and/or removable storage devices, suchas fixed disc drives, removable memory cards, optical storage, SSD orflash memory devices, network attached storage (NAS), or connections tostorage area-network (SAN) devices.

As shown, the memory 325 stores a stream manager 134. Additionally, thestorage 330 includes an operator graph 132. The stream manager 134 mayuse the operator graph 132 to route tuples to PEs 235 for processing. Asshown, the stream manager 134 also contains break manager 333. The breakmanager 333 generally allows for the definition of timing breakpointswithin the streams application. A breakpoint is generally defined as astopping point within an application for the purpose of debugging. Oncetriggered, a breakpoint will halt all processing in the application. Ina streams environment, this may include halting all processing withinall operators in the operator graph. The conditions which trigger abreakpoint traditionally must occur simultaneously, which, as discussedabove, is difficult to pinpoint in a streams application. Therefore, ina streams application, a window of tuples may be used as a referencepoint to define the “simultaneous” context within which a breakpointcondition must occur. A window is generally defined as a logicalcontainer for data tuples received at the operator which may or may nothave been processed by the operator. For example, a grouping of 1, 10,or 100 tuples may be defined to be a window within a particularoperator. The “timing breakpoints” disclosed herein are defined by thebreak manager 333, and may incorporate this window context. The timingbreakpoints may be defined to be specific to one operator, severaloperators, or may be globally defined to apply to all operators in theoperator graph 132. In some embodiments disclosed herein, the breakmanager 333 may provide a window to an operator which does not support awindow by default.

Stream computing applications may provide at least two types of windows,including tumbling windows and sliding windows. An operator may notsupport windows by default. Both tumbling and sliding windows storetuples preserving the order of arrival at the operator, but differ inhow they handle tuple evictions. Rather than keeping all tuples everinserted, windows are configured to evict expired tuples. In thisrespect, tumbling windows operate in batches; when a tumbling window isfull, all the tuples in the window are evicted. This is called a windowflush. After a tumbling window has been flushed, the window is nottriggered until the buffer 260 contains the requisite number of tuplesor a predefined period of time has elapsed. On the other hand, slidingwindows operate in an incremental fashion. When a sliding window isfull, future tuple insertions generally result in evicting the oldesttuples in the window. Triggering a new sliding window may occur as a newtuple is received, or when a predefined period of time has elapsed. Thedetails of tuple eviction in a sliding window are defined by theeviction policy. In both a tumbling and sliding window, the windowingpolicy defines a trigger policy based on a predefined number of receivedtuples or the expiration of a predefined period of time.

FIG. 4 is a flowchart depicting a method 400 for streams debuggingwithin a windowing condition, according to one embodiment disclosedherein. In some embodiments, the break manager 333 performs the steps ofthe method 400. At step 410, the break manager 333 defines a timingbreakpoint. A timing breakpoint is a breakpoint where multipleconditions need to be met, executing in some cases in separateprocesses, in some cases on different computing nodes. In someembodiments, the conditions must occur within a window of data tupleswithin the operator. In some embodiments, the conditions may need tooccur within a specified time frame, which may be defined by a window oftuples within the operators. As stated above, the breakpoint may bedefined as to a single operator, several operators, or all operators inthe operator graph 132. The definition of a timing breakpoint isdiscussed in further detail with reference to FIG. 5. At step 420, datatuples are received throughout the operator graph as the streamsapplication begins executing. At step 430, the break manager 333monitors the windows of the operators to detect the presence of theconditions which trigger the timing breakpoint. At step 440, upondetecting the presence of the condition, the break manager 333 triggersa timing breakpoint, halting execution of the streams application, andproviding a debugging environment.

FIG. 5 is a flowchart depicting a method 500 corresponding to step 410for defining a timing breakpoint, according to one embodiment disclosedherein. In some embodiments, the break manager 333 performs the steps ofthe method 500. At step 510, the break manager 333 identifies theoperators subject to the timing breakpoint. The operators subject to thetiming breakpoint may be defined by a user, or may be specified by thebreak manager 333. In some embodiments, all operators in the operatorgraph 132 may be subject to the conditions of a timing breakpoint. Inother embodiments, one operator or several operators may be subject tothe timing breakpoint. The specification of operators subject to thetiming breakpoint is essential in a streams programming environmentbecause in many embodiments, the conditions triggering the timingbreakpoint may only be detected within a window of the operator.

At step 520, the break manager 333 begins executing a loop containingsteps 530-550 for each operator subject to the timing breakpoint. Atstep 530, the break manager 333 determines whether the operator supportswindowing by default. In some embodiments, operator properties specifywhether the operator supports windowing. In other embodiments, operatormodels provide information indicating whether the operator supportswindowing. In some embodiments, providing a window for an operatorsubject to the timing breakpoint is necessary to provide a contextwithin which the break manager 333 may examine the contents of thetuples being processed by the operator to detect the presence of aspecified condition. Therefore, in some embodiments, a window providesthe timing context within which a timing breakpoint condition mustoccur. If the operator supports windowing, the break manager 333proceeds to step 550. Otherwise, the break manager 333 proceeds to step540. At step 540, the break manager 333 imposes a window upon theoperator. In imposing a window upon the operator, the break manager 333specifies parameters for the window, including, but not limited to awindow type, an eviction policy, and a trigger policy. A window type, asdescribed above, may be tumbling, sliding, or any other type of window.The window types and policies described herein are merely illustrativeand should not be considered limiting of the disclosure, as all types ofwindows and policies are contemplated. An eviction policy defines thenumber of tuples which constitute a full window to trigger processing bythe operator. A trigger policy indicates an event which triggersprocessing of the tuples in the window by the operator. Each windowingtype keeps all members in memory until a trigger is reached, which thenevicts tuples based on the eviction policy. In some embodiments, thebreak manager 333 may provide the window parameters. In otherembodiments, a user may specify the window parameters. In otherembodiments, a history of tuples flowing through the operator may bemaintained to define the window. When the operator is provided with awindowing condition, the operator must uphold the window and itsconditions when executing in debugging mode.

At step 550, the break manager 333 determines whether additionaloperators subject to the timing breakpoint remain. If more operatorsremain, the break manager 333 proceeds to step 520. If all operatorshave been processed, the break manager 333 proceeds to step 560. At step560, discussed in greater detail with reference to FIG. 6, the breakmanager 333 defines breakpoint conditions. The conditions of a timingbreakpoint are conditions which, when discovered, trigger the timingbreakpoint. One example of a timing breakpoint condition would be thepresence of a tuple attribute in a first operator window matching atuple attribute in a second operator window, where the application isconfigured to have operators process tuples sequentially. For example,in an application having operators A, B, C, D, and E, a user may definea breakpoint condition to stop the application when operator A's windowhas a tuple attribute that matches a tuple attribute in operator E'swindow.

FIG. 6 is a flowchart depicting a method 600 corresponding to step 560for defining timing breakpoint conditions, according to one embodimentdisclosed herein. In some embodiments, the break manager 333 performsthe steps of the method 600. Although depicted as a flowchart, the breakmanager 333 may perform one, several, or all of the steps of the method600 to define conditions for a timing breakpoint. At step 610, the breakmanager 333 defines a timing breakpoint condition where a tuple is beingprocessed in two operators at the same time. In some embodiments, awindow of tuples in the operator is used to define the amount of time.The window may be used as the frame of reference, as the window willcontain at most a fixed number of tuples within a specified unit oftime. As a first example, in embodiments where the streams applicationis configured to process tuples sequentially, if the break manager 333detects a unique tuple in the window of two different operators, thecondition is met. The condition would be met in such a setting becausethe presence of a unique tuple being processed by two operators atroughly the same time can be a signal that an error has occurred, as thesame tuple should not be present in the window of two operators at thesame time. As another example, the streams application may not processtuples sequentially, but tuples may share a unique attribute value, andother tuple attributes may trigger a breakpoint. For example, in abanking application, in a first operator window, a first tuple from afirst user having a unique userID may specify that the first user isexecuting a banking transaction at a first location. At about the sametime, in a second operator window, a second tuple from the first usermay specify that the first user is executing a banking transaction at asecond location, physically different from the first location. If thebreak manager 333 were to detect these conflicting locations in twooperator windows, the condition would be met. The condition would be metbecause the first user cannot physically be in two different locationsat the same time.

In one embodiment, conditions occurring in the windows of operators indifferent operator graphs may trigger a timing breakpoint. Therefore,the windows of operators in more than one operator graph may bemonitored to detect the presence of conditions which may trigger atiming breakpoint. Upon triggering the timing breakpoint, execution maybe halted in the operators of none, some, or all of the operator graphs.For example, the stream manager 134 may access the memory shared by allstream managers to monitor the contents of windows against the contentsof windows being monitored by the stream manager 134. For example, adatabase may be shared by all stream managers, and window contents maybe written by each stream manager to the database. Upon detecting, inthe shared database, tuples in windows across operator graphs which meetthe condition, the timing breakpoint may be triggered. In embodimentsemploying a hierarchical arrangement of stream managers that allow thedifferent stream managers to communicate, stream managers in thehierarchy may monitor windows in their own operator graph and share theoperator window data with the other stream managers in the hierarchy.Additionally, a higher-level stream manager in the hierarchy may monitoroperator windows across multiple operator graphs to detect the presenceof conditions which may trigger a timing breakpoint. By implementingtiming breakpoints across operator graphs, fraudulent activity may bedetected across separate operator graphs executing sales applicationsfor two different retailers when one person's credit card is being usedfor nearly simultaneous in-person transactions in one retailer'sCalifornia store and the other retailer's New York store.

At step 620, the break manager 333 defines a timing breakpoint conditionwhere a tuple in the window of an operator has an attribute valueviolating a specified threshold. This type of timing breakpointcondition occurs when a tuple has an attribute value whose values exceedspecified bounds. For example, a salary threshold may be set for thesalaries of a group of employees. The threshold may be defined by auser, or by the break manager 333. The threshold may have an upperbound, a lower bound, or both. The salary threshold may therefore bedefined as setting a $100,000 maximum for employee salaries, a $30,000minimum for employee salaries, or both. The threshold may apply to alloperators, or a given subset of operators. Therefore, when the breakmanager 333 detects a data tuple having a salary attribute of $1,000,000in an operator subject to the maximum salary timing breakpointcondition, the break manager 333 will trigger the timing breakpoint, andexecution of the application will halt.

At step 630, the break manager 333 defines a timing breakpoint conditionwhere the result of a function applied against attribute values of atleast one data tuple in the window of an operator violates a specifiedthreshold. Thus, the break manager 333 is configured to examineattribute values within a window of the operator, and performs specificfunctions on the values. The result of the function may be checkedagainst a threshold specified by a user, or specified the break manager333. For example, the break manager 333 may average the values of salarytuples to determine whether the average salary falls within a specifiedrange. As another example, the break manager 333 may set a tolerancethreshold for “bad” attribute values. If a scanner emits a particularattribute, “0” for example, as a “bad” value, 20 bad attribute values of“0” received from a scanner in a window of 100 tuples may be defined asthe timing breakpoint condition. If the break manager 333 detects morethan 20 tuples having “0” attribute values, the application may assumethat something is wrong with the scanner, and since the timingbreakpoint condition is met, application execution will halt. Theexamples provided herein are merely exemplary, as any computationalfunction may be applied to the tuple attributes to determine whether theresult of the function violates a specified threshold. Furthermore, anytype of condition may be defined to trigger a breakpoint, and thoseexamples provided with reference to FIG. 6 should not be consideredlimiting of the disclosure.

FIG. 7 illustrates a table 700 indicating whether operator windowcontents will trigger a timing breakpoint, according to one embodimentdisclosed herein. As shown, the table depicts, at a given time in column705, the contents of a window of exemplary operator A in column 710, thecontents of a window of exemplary operator B in column 715, and whetheran exemplary timing breakpoint will be triggered in column 720. In row725, an exemplary point in time T=1 is provided. Note that the timevalue merely provides a context for the contents of an operator windowat a given time. As shown in row 725, the contents of the window ofoperator A are tuples having processing ID (PID) values: {PID=100},{PID=101}, {PID=102}, and {PID=103}, and the contents of the window ofoperator B are tuples {PID=110}, {PID=111}, {PID=112}, and {PID=113}.Assume, for the contents of rows 725 and 730, the timing breakpointcondition specifies that no tuples having duplicate PIDs can be in thewindow of operator A and operator B at the same time, as the operatorsmust process all data tuples sequentially. Because, in row 725, eachwindow has unique PID attribute values, the timing breakpoint has notbeen triggered. Moving to row 730 for T=2, the contents of the window ofoperator A are still {PID=100}, {PID=101}, {PID=102}, and {PID=103},however the contents of operator B are now {PID=100}, {PID=111},{PID=112}, and {PID=113}. Because the tuple {PID=100} is present in bothoperator A and operator B, the timing breakpoint will be triggered, andthe application will halt.

In row 735, corresponding to T=3, the tuples contain salary data.Assume, for the purpose of row 735, that the timing breakpoint conditionspecifies that in the window of operator A, tuple salary attributes musthave values less than 65,000. The contents of the window of operator Ain row 735 are {Salary=45,000}, {Salary=50,000}, {Salary=55,000},{salary=42,000}, and {Salary=155,000}. Because the final tuple has asalary attribute of 155,000, greater than 65,000, the timing breakpointcondition is met, and the timing breakpoint is triggered. Tuples foroperator B are not shown because the conditions refer only to operatorA's window. In row 740, corresponding to T=4, the tuples contain valuesreceived from a sensor. Assume, for the purpose of row 740, that thesensor emits values of “0” when an error occurs. Assume further that thetiming breakpoint condition specifies that the window of operator B,which has a size of 8 data tuples, must have fewer than three readingvalues which equal “0”. As shown, the contents of operator B's window inrow 740 are {Reading=0}, {Reading=10}, {Reading=20}, {Reading=10},{Reading=10}, {Reading=0}, {Reading=0}, and {Reading=10}. Tuples foroperator A are not shown because the conditions refer only to operatorB's window. Because there are three readings in the window of operator Bhaving values which equal “0,” the condition has been satisfied, and thetiming breakpoint will be triggered.

In distributed computing, events generally do not occur at the exactsame time, meaning that breakpoints may not be triggered if thebreakpoint conditions must occur simultaneously. By defining a timingbreakpoint in a streams computing environment as described herein,streams applications developers may detect conditions which occur in agiven time frame. By examining tuples in a window of an operator, a timeframe may be defined such that a timing breakpoint may be determined toexist, allowing streams application developers to properly debug streamsapplications.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present disclosure. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1.-9. (canceled)
 10. A computer program product, comprising: acomputer-readable storage medium having computer-readable program codeembodied therewith, the computer-readable program code comprising:computer-readable program code configured to provide a plurality ofprocessing elements comprising one or more operators, the operatorsconfigured to process streaming data tuples by operation of one or morecomputer processors; computer-readable program code configured toestablish an operator graph of a plurality of operators, the operatorgraph defining at least one execution path in which a first operator ofthe plurality of operators is configured to receive data tuples from atleast one upstream operator and transmit data tuples to at least onedownstream operator; computer-readable program code configured to definea breakpoint comprising a condition, the condition based on attributevalues of data tuples in a window of at least one operator, wherein thewindow comprises a plurality of data tuples in an operator; andcomputer-readable program code configured to, upon detecting occurrenceof the condition, trigger the breakpoint to halt processing by each ofthe plurality of operators in the operator graph.
 11. The computerprogram product of claim 10, wherein the condition comprisesdetermining, based on unique tuple attributes, that a tuple beingprocessed by a first operator is also being processed by a secondoperator.
 12. The computer program product of claim 10, wherein thecondition comprises identifying at least one data tuple containing anattribute value violating a specified threshold.
 13. The computerprogram product of claim 10, wherein the condition comprises determiningthat a result of a function applied against attribute values of at leastone data tuple violates a specified threshold.
 14. The computer programproduct of claim 10, wherein triggering the breakpoint comprises:receiving a plurality of data tuples in the operator graph; monitoringthe windows of the operators for occurrence of the condition; and upondetecting the occurrence of the condition, halting execution in each ofthe plurality of operators in the operator graph.
 15. The computerprogram product of claim 10, wherein the condition must occur within aspecified amount of time, wherein the time is defined by a specifiedwindow of data tuples within the operator.
 16. The computer programproduct of claim 10, wherein the condition is based on attribute valuesof data tuples in a first window in a first operator graph and attributevalues of data tuples in a second window in a second operator graph,wherein triggering the breakpoint halts processing in the first operatorgraph.
 17. The computer program product of claim 10, further comprisingimposing a window on an operator not configured to maintain a window ofdata tuples.
 18. A system, comprising: one or more computer processors;and a memory containing a program, which when executed by the one ormore computer processors is configured to perform an operation, theoperation comprising: providing a plurality of processing elementscomprising one or more operators, the operators configured to processstreaming data tuples by operation of one or more computer processors;establishing an operator graph of a plurality of operators, the operatorgraph defining at least one execution path in which a first operator ofthe plurality of operators is configured to receive data tuples from atleast one upstream operator and transmit data tuples to at least onedownstream operator; defining define a breakpoint comprising acondition, the condition based on attribute values of data tuples in awindow of at least one operator, wherein the window comprises aplurality of data tuples in an operator; and upon detecting occurrenceof the condition, triggering the breakpoint to halt processing by eachof the plurality of operators in the operator graph.
 19. The system ofclaim 18, wherein the condition comprises determining, based on uniquetuple attributes, that a tuple being processed by a first operator isalso being processed by a second operator.
 20. The system of claim 18,wherein the condition comprises identifying at least one data tuplecontaining an attribute value violating a specified threshold.
 21. Thesystem of claim 18, wherein the condition comprises determining that aresult of a function applied against attribute values of at least onedata tuple violates a specified threshold.
 22. The system of claim 18,wherein triggering the breakpoint comprises: receiving a plurality ofdata tuples in the operator graph; monitoring the windows of theoperators for occurrence of the condition; and upon detecting theoccurrence of the condition, halting execution in each of the pluralityof operators in the operator graph.
 23. The system of claim 18, whereinthe condition must occur within a specified amount of time, wherein thetime is defined by a specified window of data tuples within theoperator.
 24. The system of claim 17, wherein the condition is based onattribute values of data tuples in a first window in a first operatorgraph and attribute values of data tuples in a second window in a secondoperator graph, wherein triggering the breakpoint halts processing inthe first operator graph.
 25. The system of claim 18, further comprisingimposing a window on an operator not configured to maintain a window oftuples.